238 BIOLOGY OF THE SEAS OF THE U.S.S.R. 



similar in its distribution in the Kara Sea to the fourth, which comes also from 

 the north, but from the warm Atlantic intermediate layer. 



The former may be said to include Amphimelissa setosa, Amallophora magna, 

 Chiridius obtusifrons, Euchaeta glacialis, Fritillaria polaris, the fourth group 

 — the radiolarian Pectacantha oikiskos, the jelly-fish Homoeonema platygonon, 

 the crustaceans Euchaeta norvegica, Heterorhabdus norvegicus, Thysanoessa 

 longicaudata, Themisto abyssorum and others (Fig. 103). 



A comprehensive study of the zooplankton of the Vilkitsky Strait led 

 M. Virketis (1944) to the conclusion that members of the zooplankton penetrate 

 this region both from the west and from the east. Small numbers of brackish- 

 water forms reach it from the Kara Sea along the shores, while the Atlantic 

 forms arrive from the Barents Sea through the open parts of the Strait 

 {Salpingella acuminata and Oithona atlantica). The Arctic-basin forms 

 {Amphimelissa setosa, Euchaeta glacialis, Frittilaria polaris) and the Atlantic 

 forms {Sticholonche zanglea, Thysanoessa longicaudata, Euchaeta norvegica, 

 Aglantha digitalis and probably Themisto abyssorum enter from the east. In 

 the western part of the Strait the influence is more strongly felt of the brackish- 

 water forms chiefly carried in by surface currents from the west, and in the 

 eastern part of the Strait that of the Atlantic forms mainly brought in with 

 the deep waters from the northeast. 



Quantitative distribution of plankton. In places where the influence of the Ob- 

 Yenisey waters is at its greatest, in the upper, fresher layers, plankton acquires 

 a completely fresh-water character (Cladocera, Rotatoria, Copepoda). In 

 the brackish waters there predominate the brackish forms Limnocalanus 

 grimaldii, Drepanopus bungei, Pseudocalanus major, Derjuginia tolli, Lenicellu 

 calanoides. 



Quantitatively the richest forms of the Kara Sea plankton are the Cope- 

 poda, namely Calanus finmarchicus (four-fifths of the total biomass) and 

 Oithona similis and Pseudocalanus elongatus (one-fifth of the total biomass). 

 Appendicularia (Fritillaria and Oikopleura) and Chaetognatha {Sagitta ele- 

 gans) are also of great significance. At times they form the largest biomass. 

 Sometimes the polychaete larvae acquire a very important place in the plank- 

 ton biomass. In the most diluted southern parts of the Sea Copepoda biomass 

 is inferior to that of the Rotifera (mainly Synchaeta) and Cladocera. 



The average quantitative significance of the separate groups of the Kara 

 Sea zooplankton is given in Table 102, due to V. Bogorov (1944, 1946). 



Jashnov (1940) considers that the average plankton biomass of the western 

 half of the Sea is 4-5 tons/km 2 , and of the total Sea in summer it is 5 million tons. 



Benthos 



Bottom flora. The phytobenthos of the Kara Sea is represented by only 55 

 forms, which is less than a third of the specific composition of the Barents Sea 

 algae {Table 103). 



Thus, in contrast to the Barents Sea, the bottom flora of the Kara Sea is 

 qualitatively much poorer than its bottom fauna. This results primarily from 

 the peculiar conditions of the Kara Sea. 



